INTERNAL MULTIBAND ANTENNA

• US 20060170600A1
• Filed: 04/13/2006
• Published: 08/03/2006
• Est. Priority Date: 10/20/2003
• Status: Active Grant

• Current Assignee: Pulse Finland Oy (Yageo Corporation)
• Original Assignee: LK Products Oy (Yageo Corporation)
• Inventors: Korva, Heikki
• Granted Patent: US 7,256,743 B2
• Time in Patent Office: Days
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/244 extendable from a housing along a given path
• CPC Class Codes: H01Q 5/371 Branching current paths
• CPC Class Codes: H01Q 5/378 Combination of fed elements with parasitic elements
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence

Abstract

The invention relates to an internal multiband antenna intended for small-sized radio devices, and a radio device with such an antenna. The basic structure of the antenna is a two-band PIFA. A parasitic element (230) is added to it inside the outline of the radiating plane (220) of the PIFA, e.g. in the space (229) between the conductor branches (221, 222) of the radiating plane. The parasitic element extends close to the feeding point (FP) of the antenna, from which place it is connected to the ground plane of the antenna with its own short-circuit conductor (235). The structure is dimensioned so that the resonance frequency based on the parasitic element comes close to the one resonance frequency of the PIFA, thus widening the corresponding operating band, or a separate third operating band is formed for the antenna with the parasitic element. Because the parasitic element is located in the central area of the radiating plane and not in its peripheral area, the radio device user'"'"'s hand does not significantly impair the matching of the antenna on an operating band which has been formed by the parasitic element. In addition, when the resonance frequency based on the parasitic element is on the upper operating band, the matching of the antenna also improves on the lower operating band.

Claims

1. An internal multiband antenna of a radio device, which antenna has at least a first and a second operating band and comprises a ground plane, a radiating plane and a radiating parasitic element electromagnetically coupled to the radiating plane, which radiating plane is at a feeding point connected to antenna port of the radio device and at a first short-circuit point to the ground plane, and is divided into a first and a second conductor branch as viewed from the first short-circuit point, and which parasitic element is at a second short-circuit point connected to the ground plane, wherein

the first conductor branch together with the surrounding antenna parts forms a resonator having a natural frequency in said first operating band

the second conductor branch together with the surrounding antenna parts forms a resonator having a natural frequency in said second operating band, and

the parasitic element together with the surrounding antenna parts forms a resonator having a natural frequency in some operating band of the antenna, said feed point being close to the second short-circuit point, and the parasitic element being located substantially on the same geometric plane as the radiating plane, in its inner area.

2. A multiband antenna according to claim 1, the electromagnetic coupling between the radiating plane and the parasitic element being for the most part caused by a predominantly inductive coupling between a first portion of the parasitic element, as viewed from the second short-circuit point, and the radiating plane.

3. A multiband antenna according to claim 1, the electromagnetic coupling between the radiating plane and the parasitic element being for the significant part caused by a predominantly capacitive coupling between opposite end of the parasitic element as viewed from the second short-circuit point, and the electrically most distant portion of the first conductor branch as viewed from the first short-circuit point, in order to reduce the significance of coupling between the parasitic element and the second conductor branch.

4. A multiband antenna according to claim 1, said inner area being confined by both the first and the second conductor branch.

5. A multiband antenna according to claim 1, wherein the second operating band of the antenna is its upper operating band, and the natural frequency of the resonator based on the parasitic element is in said upper operating band to widen it.

6. A multiband antenna according to claim 1, which further has a third operating band, the natural frequency of the resonator based on a parasitic element being in said third operating band.

7. A multiband antenna according to claim 1, the radiating plane and the parasitic element being separate pieces of sheet metal.

8. A multiband antenna according to claim 1, the radiating plane and the parasitic element being conductive areas on a surface of a dielectric plate.

9. A radio device having at least a first and a second operating band and comprising an internal multiband antenna, which has a ground plane, a radiating plane and a radiating parasitic element electromagnetically coupled to the radiating plane, which radiating plane is at a feed point connected to a antenna port of the radio device and at a first short-circuit point to the ground plane and, as viewed from the first short-circuit point the radiating plane, is divided into a first and a second conductor branch, and which parasitic element is connected to the ground plane at a second short-circuit point, wherein

the first conductor branch together with the surrounding antenna parts forms a resonator having a natural frequency in said first operating band

the second conductor branch together with the surrounding antenna parts forms a resonator having a natural frequency in said second operating band, and

the parasitic element together with the surrounding antenna parts forms a resonator having a natural frequency n some operating band of the antenna, said feed point being close to the second short-circuit point, and the parasitic element being located substantially on the same geometric plane as the radiating plane, in its inner area.